The present invention relates to a semiconductor processing apparatus, and more particularly, to a semiconductor processing apparatus which predicts processing results to improve the operating rate and reliability of the apparatus and a method of monitoring and/or controlling the semiconductor processing apparatus.
In recent years, the dimensions of semiconductor devices have been miniaturized more and more, so that a severe manufacturing dimension accuracy is required to such an extent that a gate electrode of 0.1 xcexcm or smaller should be processed in a dimensional accuracy of 10% or less. On the other hand, in a semiconductor manufacturing apparatus for processing a semiconductor wafer using heat and plasma and reaction products, resulting from chemical reactions within the apparatus, are attached and remain on inner walls of the apparatus. Such reaction products change a wafer processing state in the apparatus over time. For this reason, as a number of wafers are sequentially processed by the semiconductor manufacturing apparatus, the shape of semiconductor devices on wafers gradually changes to cause deteriorated performance. To accommodate this problem, generally, various countermeasures have been taken. For example, the inner walls of the chamber are cleaned using plasma to remove products attached thereon, or the walls of the chamber are heated so that products are less likely to adhere on the inner walls. However, in most cases, such countermeasures are not perfect, inevitably resulting in a gradual change in the shape of processed semiconductor devices. For this reason, the manufacturing apparatus must undergo replacement of parts and wet cleaning before the shape of processed devices changes so as to cause a problem. In addition, fluctuations in a variety of states of the apparatus involve in variations in the shape of devices processed on wafers, other than deposited films. To address these problems, there have been created techniques for detecting a change in a processing state within a semiconductor manufacturing apparatus and feeding back the result of detection to the input of the semiconductor manufacturing apparatus to maintain the processing state constant.
Such a method of monitoring fluctuations in plasma processing is disclosed, for example, in JP-A10-125660.This official document shows a method of predicting the performance of an apparatus and diagnosing the state of plasma using an equation representing the relationship between plasma processing characteristics and electric signals generated in the apparatus. Specifically, JP-A-10-125660 discloses a method of deriving an approximate expression which represents the relationship between three electric signals and the plasma processing characteristics of the apparatus through multiple regression. Another example is disclosed in JP-A-11-87323. A method disclosed in JP-A-11-87323 adapts a general detection system having a multiplicity of existing detectors mounted thereon to a semiconductor manufacturing apparatus to monitor the state of the apparatus from a correlation signal of signals detected by the detectors. Specifically, the correlation signal is generated by a calculation based on the ratio of six electric signals. A further example is disclosed in U.S. Pat. No. 5,658,423. This U.S. patent discloses a method of monitoring the state of an apparatus by capturing a number of signals from a light and a mass analyzer to generate a correlation signal for monitoring. The correlation signal is generated using a principal component analysis.
However, the method disclosed in JP-A-10-125660 fails to perform a successful prediction using the multiple regression when there are a large number of sensor data for monitoring the apparatus since explanatory variables include a large number of signals which are not related to the processing performance intended for the prediction. The method disclosed in JP-A-11-87323 in turn is a general method which performs the diagnosis using a signal correlated to a multiplicity of detected signals from a multiplicity of known detecting means, wherein the correlation is established by taking the ratio of several signals, just as conventional approaches. This method, therefore, would encounters difficulties in applying to a specific system for accurately monitoring the state of a semiconductor manufacturing apparatus which can take a variety of states depending on a large number of causes for fluctuations. Unlike the foregoing methods, U.S. Pat. No. 5,658,423 discloses a method of monitoring the state of plasma by analyzing a principal component of a large amount of data monitored from an apparatus to capture fluctuations in the state of the apparatus. However, semiconductor manufacturing apparatus for use in actual mass production would not work well only with a concept of adapting a general statistic processing method as disclosed. For example, it is unknown in most cases how a change in the principal component will cause what kind of result in the processing.
It is an object of the present invention to provide a semiconductor processing apparatus and method which monitor a processing state to detect faulty processing or predict processing results based on a monitored output to improve the operating rate and reliability of the semiconductor processing apparatus for processing a variety of types of devices.
According to an aspect of the present invention, a semiconductor device processing apparatus includes a sensor for monitoring a processing state of the semiconductor processing apparatus, processing result input means for inputting measured values for processing results of a semiconductor wafer processed by the semiconductor processing apparatus, a model equation generation unit relying on sensed data acquired by the sensor and the measured values to generate a model equation for predicting a processing result using the sensed data as an explanatory variable, a processing result prediction unit for predicting a processing result based on the model equation and the sensed data, and a process recipe control unit for comparing the predicted processing result with a previously set value to control a processing condition of the semiconductor processing apparatus such that a deviation between the predicted processing result and the previously set value is corrected.
With the foregoing configuration, according to the present invention, monitored data is acquired by the sensor from the semiconductor processing apparatus to generate a model equation which is used to predict processing results before measuring processing results of samples or without measuring the processing results, thereby improving the operating rate and reliability of the semiconductor processing apparatus.